1. Field of the Invention
The present invention relates to a polymer electrolyte membrane, a method of manufacturing the same, and a fuel cell including the polymer electrolyte membrane.
2. Description of the Related Art
Fuel cells may be classified according to the type of electrolyte used therein. Types of fuel cells include polymer electrolyte membrane fuel cells (PEMFCs), phosphoric acid fuel cells, molten carbonate fuel cells, solid oxide fuel cells, and others. The operating temperatures of fuel cells and constituent materials thereof vary depending on the electrolyte type.
According to a method of supplying fuel to an anode, fuel cells can be classified into external reforming type fuel cells in which fuel is supplied to the anode after being converted into hydrogen enrichment gas by a fuel reformer, and internal reforming type fuel cells in which fuel in liquid or gaseous state is directly supplied to the anode.
A representative example of a direct fuel supply type fuel cell is a direct methanol fuel cell (DMFC). In a DMFC, an aqueous methanol solution is used as fuel, and a proton conductive polymer electrolyte membrane is used as an electrolyte. Accordingly, a DMFC is a kind of PEMFC.
PEMFCs are small and light but can realize high output density. Moreover, PEMFCs simplify the structure of a power generating system.
A PEMFC is usually formed of an anode (a fuel cell), a cathode (oxidizer electrode), and a polymer electrolyte membrane disposed between the anode and the cathode. The anode of a PEMFC includes a catalyst layer to facilitate oxidization of fuel, and the cathode of a PEMFC includes a catalyst layer to facilitate reduction of an oxidizer.
The polymer electrolyte membrane of a PEMFC functions as an ion conductor for hydrogen ions to move from the anode to the cathode and as a separator to physically separate the anode and the cathode. Accordingly, the polymer electrolyte membrane needs to have good ion conductivity, electrochemical stability, high mechanical intensity, and thermal stability at operating temperatures, and be easy to be made thin.